Commentary Aristotle Metaphysics
Lecture 10. The Platonic theory of ideas
After the philosophies described came the system of Plato, which followed them in many respects, but also had other theses of its own in addition to the philosophy of the Italians. For Plato, agreeing at the very beginning with the opinions of Cratylus and Heraclitus that all sensible things are always in a state of flux, and that there is no scientific knowledge of them, also accepted this doctrine in later years. However, when Socrates, concerning himself with moral matters and neglecting nature as a whole, sought for the universal in these matters and fixed his thought on definition, Plato accepted him because of this kind of investigation, and assumed that this consideration refers to other entities and not to sensible ones.
For, according to him, it is impossible that there should be a common definition of any one of these sensible things that are always changing. Such entities, then, he called ideas or forms, and he said that all sensible things exist because of them and in conformity with them, for there are many individuals of the same name because of participation in these forms. With regard to participation, he changed the name, for while the Pythagoreans say that things exist by imitation of numbers, Plato says that they exist by participation, changing the name. Yet what this participation or imitation of forms is they commonly neglected to investigate.
Further, he says that besides sensible things and ideas there are the objects of mathematics, which are an intermediate genus. These differ from sensible things in being eternal and immobile; from the ideas in that there are many alike, whereas each idea is itself only one.
And since the forms are the causes of other things, he thought that the elements of these are the elements of all existing things. Hence, according to him, the great and small are principles as matter, and the one as substance. For it is from these by participation in the one that the ideas are numbers.
Yet Plato said that the one is substance and that no other being is to be called one, just as the Pythagoreans did. Also like them, he said that numbers are the causes of real substance.
But to posit a dyad in place of the indeterminate one, and to produce the unlimited out of the great and small, is peculiar to him. Moreover, he says that numbers exist apart from sensible things, whereas they say that things themselves are numbers. Further, they do not maintain that the objects of mathematics are an intermediate class.
Therefore, his making the one and numbers to exist apart from things and not in things (as Pythagoreans did), and his introducing the separate forms, was due to his investigation into the ideas of things. For the earlier philosophers were ignorant of dialectic.
But his making the dyad to be a different nature was due to the fact that all numbers, with the exception of prime numbers, are naturally generated from the number two as a matrix.
Yet what happens is the contrary of this. For this view is not a reasonable one, because the Platonists produce many things from matter but their form generates only once.
And from one matter one measure seems to be produced, whereas he who induces the form, even though he is one, produces many measures. The male is also related to the female in a similar way, for the latter is impregnated by one act, but the male impregnates many females. And such are the changes in these principles. Concerning the causes under investigation, then, Plato defines them thus.
From the foregoing account it is evident that Plato used only two causes: one being the whatness of a thing, and the other, matter. For the forms are the cause of the whatness in other things, and the one is the cause of the whatness in the forms.
It is also evident what the underlying matter is of which the forms are predicated in the case of sensible things, and the one in the case of the forms—it is this duality, the great and small.
Moreover, he assigned the cause of good and evil to these two elements, one to each of them, which is rather a problem, as we say that some of the first philosophers (such as Empedocles and Anaxagoras) have attempted to investigate.
Plato and form
151. Having given the opinion of the ancient philosophers about the material and efficient cause, he gives a third opinion, that of Plato, who was the first to clearly introduce the formal cause. This is divided into two parts.
First, he gives Plato’s opinion.
Second, from all of the foregoing remarks he makes a summary of the opinions which the other philosophers expressed about the four genera of causes, at we have examined.
First, he gives Plato’s opinion about the substances of things;
second, his opinion about the principles of things, at and since the forms.
First, he gives Plato’s opinion insofar as he posited ideas;
and second, insofar as he posited intermediate substances, the separate mathematical entities, at further, he says.
He first says that after all the foregoing philosophers came the system of Plato, who immediately preceded Aristotle; for Aristotle is considered to have been his disciple. And even if Plato followed in many respects the natural philosophers who preceded him, such as Empedocles, Anaxagoras, and the like, he nevertheless had certain other doctrines of his own in addition to those of the preceding philosophers, because of the philosophy of the Italians, or Pythagoreans. For insofar as he was devoted to the study of truth he sought out the philosophers of all lands in order to learn their teachings. Hence he came to Tarentum in Italy, and was instructed in the teachings of the Pythagoreans by Archytas of Tarentum, a disciple of Pythagoras.
152. Now Plato would seem to follow the natural philosophers who lived in Greece; of this group some of the later members held that all sensible things are always in a state of flux, and that there can be no scientific knowledge of them (which was the position of Heraclitus and Cratylus). And since Plato became accustomed to positions of this kind from the very beginning, and agreed with these men in this position, which he acknowledged to be true in later years, he therefore said that scientific knowledge of particular sensible things must be abandoned.
And Socrates (who was Plato’s master and the disciple of Archelaus, a pupil of Anaxagoras), because of this position which arose in his time—that there can be no science of sensible things—was unwilling to make any investigation into the nature of physical things, but busied himself only with moral matters. And in this field he first began to investigate what the universal is, and to insist upon the need for definition.
153. Hence, Plato, being Socrates’ pupil, accepted Socrates, that is, followed him, and adopted this method for the purpose of investigating natural beings. He did so believing that in their case the universal in them could successfully be grasped and a definition be assigned to it, with no definition being given for any sensible thing. For, since sensible things are always changing, or being changed, no common intelligible structure can be assigned to any of them.
Every definition must conform to each thing defined and must always do so, and thus each requires some kind of immutability. Hence universal entities of this kind, which are separate from sensible things and that to which definitions are assigned, he called the ideas or forms of sensible things. He called them ideas, or exemplars, inasmuch as sensible things are made in likeness to them; and he called them forms inasmuch as sensible things have substantial being by participating in them. Or he called them ideas inasmuch as they are principles of being, and forms inasmuch as they are principles of knowledge.
Hence all sensible things have being because of them and in conformity with them. They have being because of the ideas insofar as the ideas are the causes of the being of sensible things, and in conformity with them insofar as they are the exemplars of sensible things.
154. The truth of this is clear from the fact that many individuals of the same name are attributed to one form alone—that is, there are many individuals which have the same form predicated of them, and predicated by participation. For the form or idea of man is the specific nature itself by which there exists man essentially.